pytest: are pytest_sessionstart() and pytest_sessionfinish() valid hooks?

Question

are pytest_sessionstart(session) and pytest_sessionfinish(session) valid hooks? They are not described in dev hook docs or latest hook docs

What is the difference between them and pytest_configure(config)/pytest_unconfigure(config)?

In docs it is said:

pytest_configure(config)called after command line options have been parsed. and all plugins and initial conftest files been loaded.

and

pytest_unconfigure(config) called before test process is exited.

Session is the same, right?

Thanks!

Answer 1

The bad news is that the situation with sessionstart/configure is not very well specified. Sessionstart in particular is not much documented because the semantics differ if one is in the xdist/distribution case or not. One can distinguish these situations but it's all a bit too complicated.

The good news is that pytest-2.3 should make things easier. If you define a @fixture with scope="session" you can implement a fixture that is called once per process within which test execute.
For distributed testing, this means once per test slave. For single-process testing, it means once for the whole test run. In either case, if you do a "--collectonly" run, or "-h" or other options that do not involve the running of tests, then fixture functions will not execute at all.

Hope this clarifies.